This invention relates to infant incubators and, more specifically, to a heated humidifier for humidifying the air delivered to the infant compartment within which the infant is positioned.
Generally it is advantageous to humidify the heated air that is delivered to an infant compartment in caring for that infant and current incubators provide various methods of carrying out that humidification.
One type of humidifier currently in use with infant incubators utilizes a passive water supply that is not heated and the warm air is passed over the surface to pick up the water vapor. This type of humidifier is, however, not extremely efficient since the lack of active heating of the water in the humidifier limits considerably the amount of water vapor that is available to be picked up by the stream of air delivered to the infant compartment. In addition, such humidifiers are also very dependent upon the particular setting of the incubator, the ambient temperature and the humidity of the nursery within which the incubator is located.
Another type of humidifier for humidifying such air is shown and described in Air Shields U.S. Pat. No. 5,242,375 and which includes a flat heater positioned beneath an evaporation tray to heat the water to enhance the release of vapor for introduction into the air stream delivered to the infant. It is quite typical to utilize such heaters positioned beneath the volume of water to heat the water and where the heated stream of air to the patient is first passed over the upper surface of the heated water where it picks up the water vapor to deliver the humidified air to the infant.
Again, however, there are shortcomings of the beneath the water reservoir arrangement. First, the water reservoir must be a fairly substantial volume to avoid the continual depletion of the water and thus the need for attending personnel to continuously refill the reservoir. Due to the large volume of water, therefore, the entire volume must be heated from the bottom, thus a considerable amount of energy is required and the response time to changes desired in the degree of humidification is fairly long. The control loop is relatively long and overshoots in humidity are common.
Additionally, with the heater located beneath the reservoir, the container for holding the quantity of water must be a specialized container since the bottom of the container must be of a good heat conductive material. The preferable material for reservoir containers is plastic that is relatively transparent so that the user can visually ascertain the level of the water. Also, of course, a molded single piece plastic container is inexpensive to produce.
A problem is, therefore, that the plastic containers cannot be directly heated through a plastic bottom and therefore such containers require a heat conductive material such as metal to actually transmit the heat into the water. Such containers, therefore, must be made of different materia, that is, plastic sides with a metallic bottom, and the juncture between the metal material and the plastic material is a potential source of leaks and causes problems in removal for cleaning. Also, obviously, the addition of a special material at the bottom of the reservoirs creates additional expense over that of producing the entire reservoir container from a single, transparent, moldable plastic material.
Accordingly, apart from the inefficiencies of providing heat to the very bottom of the large volume of water where the water vapor is being generated and removed from the upper surface only of the reservoir, the construction of the reservoir container is fairly costly and specialized, requiring a heat conductive bottom to allow the flow of heat into the water.